Proposed 2013 Updates to Alberta’s Air Quality Model Guideline

Frauke Spurrell, Wally Qiu

and David Lyder

CPANS Luncheons November 2012

Purpose of Air Quality Model Guideline

The AQMG is used to ensure consistency in the use of dispersion models in air quality assessments.

The objectives are to:– Provide for uniform benchmarking,– Provide a structured approach to selection and

application of models,– Ensure that there is a sound scientific basis for the

use of alternatives, when alternatives are appropriate, and

– Detail the required content of assessments submitted to the department.

Levels of Modelling

There are three levels of assessment:

– Screening assessment - this is utilized to determine an initial impression of the highest concentrations that are likely to occur.

– Refined assessment – due to its higher level of sophistication, more closely estimates actual air quality impacts of single or multiple sources.

– Advanced assessment - treats specific processes in greater detail using an alternative or modified model. Justification for use and modelling details should be verified with AENV prior to submission.

Accepted Regulatory Models

Analysis Recommended Models

Screening AssessmentAERSCREEN - This is a single

source model which uses worst-case meteorological data.

Refined Assessment

AERMOD-PRIME - This is a multi-source steady-state plume model.

CALPUFF - This is a multi-layer, multi-species, non-steady-state, puff dispersion model that can simulate the effects of time- and space-varying meteorological conditions.

Proposed Changes to AQMG: Baseline Concentrations, Inputs and

Outputs

Baseline Input Output

Screening

• 99.9th % of non-blank ambient background• Max operating for all sources in 5 km for all averaging periods except for annual averaging (then use annual average)

• Proposed max hourly operating except for annual average (then use proposed annual operating)

• 99.9th % for all averaging periods (no removal of hourly data for longer averaging periods)

Refined/advanced

• 90th % of non-blank ambient background• As above

• As above • As above

Proposed Changes to AQMG: NO2/NOx Conversion Methods

• OLM Method• Hourly time series of O3 for each month added into

Appendix D (no longer maximum seasonal rates)

• Different series for urban and rural settings

 • ARM Method

• Specifications for selecting appropriate downwind monitors to determine equilibrium NO2/NOx ratio

• 0.7 default value if no monitoring data available

Proposed Changes to AQMG: Meteorological Data

• Meteorology - Screening• More sophisticated meteorological grid provided inside

of AERSCREEN (MAKEMET)

• Meteorology – Refined/Advanced• One year of on-site data (not modelled meteorology)

– 90% complete

– Fill in upper air data

• Five years of modelled data (2002 – 2006) as provided by ESRD

• No other data sets accepted

Proposed Changes to AQMG: Models

• Use of AERSCREEN as recommended model for screening purposes

• A formula is provided for calculating alternate averaging periods

• Added guidance on CALMET switch settings and version

• Use the current version and recommended model switches available on TRC Solutions website

• Deviation from default requires discussion prior to modelling and additional modelling (see CALPUFF)

• Use as much prognostic data as possible; CALMET may not be used on its own

Proposed Changes to AQMG: Models

• CALPUFF model• Use current version available on TRC Solutions website

and recommended model switches (default model)

• Deviation from current model with recommended switches requires duplicate modelling with default model for comparative purposes (maximum, distribution, time series, statistics); the Director still has the right to select default modelling results

Next Steps…

• The revised Air Quality Modelling Guideline is being prepared for posting

• There will be a 60 day public comment period once the updated guideline is posted